27-10-03 12:53
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Under certain circumstances the I2C speed is lower that desired. This behaviour depends on the termination (pull-up resistor) and on the real capacitances of the I2C bus. If the termination is too high (e.g. 10k) and the capacitance on the bus is high too (e.g. > 200pF) this will lead to an increasing time of the rising edge on the SCL line and the high level on the bus will be achieved later. Hence the cycle duration will increase and the frequency will getting lower.
One solution is a lower termination to achieve the correct I2C speed (I2C Studio: Options->Board->Termination). 2kOhm could e.g. be a good choice for 5V I2C bus systems - see NPX (formerly Philips Semiconductors) I2C specifaction for details.
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